Identification of Operators and Promoters That Control SXT Conjugative Transfer

Abstract

ABSTRACT Transfer of SXT, a Vibrio cholerae -derived integrating conjugative element that encodes multiple antibiotic resistance genes, is repressed by SetR, a λ 434 c I-related repressor. Here we identify divergent promoters between s086 and setR that drive expression of the regulators of SXT transfer. One transcript encodes the activators of transfer, setC and setD . The second transcript codes for SetR and, like the c I transcript of lambda, is leaderless. SetR binds to four operators located between setR and s086 ; the locations and relative affinities of these sites suggest a model for regulation of SXT transfer.